I too appreciate our exchanges. I especially appreciate that you offer more than an "I agree" or "Amen." It is good for the head to have a bit more to chew on than that.

One of the interesting things to ponder, at least in my mind, is how one's foundational paradigm impacts everything else he understands. You and I have I, I think, have differing foundational premises. Because of that we tend to interpret the same concepts differently. I am thankful that, so far anyway, we have been able to differ pleasantly. :-)

First, regarding the term, Jews, While it might be true that the term Jew is derived from the word Judah, not every etymologist agrees. It may not have any relationship to Judah. It is an English word, made to refer to the people of Israel and has a few potential roots, Judah being just one of them. Let's assume though, that it does derive from Judah, By the time we find the term used in the Bible, it is obviously being used to refer to more than the tribe of Judah. Jesus was born more than the King of Judah, but the King of Israel. Yet we find the term "King of the Jews" used repeatedly in the N.T.
1 Corinthians 10:32 (KJV)
Give none offence, neither to the Jews, nor to the Gentiles, nor to the church of God:
The word Jews in this verse obviously references all of the people in Israel just as Gentiles references all of the nations not belonging to Israel.
I used the word Jews in the most normal sense today, not in the strictest sense.

Regarding observing a group observing the Feast of Tabernacles today - I think that is an excellent idea! There would be great insights to be gleaned. I would suggest though, that they would not be Biblical insights. The Jews have long ago lost any real Biblical insights and merely practice tradition. After these many thousands of years I do not believe they have any better understanding of how the Feast of Tabernacles is to be practiced than I do because I have the only fully preserved set of instructions in my Bible.

I do not believe "we"who are Christians today, will be keeping the Feast of Tabernacles in the Millennial Kingdom. We will have been changed, we will have taken the likeness of Christ and will be joint heirs with Him. We will rule with Him. I do believe that, for the 1000 years of the Millennial Kingdom, the Jews (who survived the seven year Tribulation and the judgment in the valley) will observe Temple related holy days and feasts. I can assume that would include the Feast of Tabernacles. But whatever Temple practices they have will have a different significance because of the presence of Jesus Christ. Every holy day, feast, and sacrifice was a type of Jesus Christ and finds its fulfillment in Jesus. None of them are necessary today - or in the Kingdom - because they have been finished in the work of Christ.